We are pleased to announce that distinguished climate change expert Amir AghaKouchak will give two special lectures on 18th and 19th May. Amir AghaKouchak is a professor at the University of California, Irvine. He is known for his contributions to analysis and understanding of natural hazards and their societal impacts, including droughts, floods, heat waves, and the interactions between inter-related compounds. His research has resulted in many well-cited publications in high-ranking journals including nature, such as AghaKouchak et al., (2018, 2015b, 2015a), Cheng et al., (2014) and Zscheischler et al. (2018).
Special Lecture 1:
Nonstationary and Multivariate Analysis in Hydrology and Climate Studies on Wednesday, 18th May, 2 pm in D218
Special Lecture 2:
Compound hazards in a warming climate on Thursday, 19th May, 2 pm in room ZI.
This talk targets a general audience, and everybody is welcome to attend.
Details
Special Lecture 1: Nonstationary and Multivariate Analysis in Hydrology and Climate Studies on Wednesday, 18th May, 2 pm in D218
Evolving climate conditions and anthropogenic factors, such as CO2 emissions, urbanization and population growth, can cause changes in weather and climate extremes. Most current risk assessment models rely on the assumption of stationarity (i.e., no temporal change in statistics of extremes). Most nonstationary modeling studies focus primarily on changes in extremes over time. In the first part of this presentation, the Process-informed Nonstationary Extreme Value Analysis (ProNEVA) will be introduced as a generalized tool for incorporating different types of physical drivers (i.e., underlying processes), stationary and nonstationary concepts, and extreme value analysis methods (i.e., annual maxima, peak-over-threshold).
The second part of the presentation focuses on multivariate analysis which is widely used in hydrology and climate studies. Here, the Multivariate Copula Analysis Toolbox (MvCAT) will be introduced which includes a wide range of copulas with different levels of complexity. MvCAT employs Bayesian analysis with a residual-based Gaussian likelihood function for inferring the parameters of copulas, and estimate the underlying uncertainties. The interesting features of MvCAT is threefold: (a) providing a Bayesian framework to approximate the predictive uncertainties of copulas, (b) introducing a hybrid Markov Chain Monte Carlo (MCMC) approach designed for numerical estimation of the posterior distribution of copula parameters, and (c) enabling the community to explore a wide range of copulas and evaluate them relative to the fitting uncertainties. The commonly used local optimization methods often get trapped in local minima. MvCAT addresses this limitation and provides a framework for robust dependence analysis. MvCAT also allows evaluating uncertainties relative to length of record, which is fundamental to a wide range of applications such as multivariate frequency analysis. After an overview of MvCAT, example applications will be provided on: (a) multivariate flood frequency analysis; (b) compounding effects of ocean and terrestrial flooding in coastal areas; (c) linking heatwaves and mortality; and (d) drought-fire relationship.
Special Lecture 2: Compound hazards in a warming climate on Thursday, 19th May, 2 pm in room ZI.
Ground-based observations and model simulations show substantial increases in extreme events including rainfall events, droughts, wildfires, hot spells and heatwaves. A key step toward improving our societal resilience is to identify emerging patterns of climate extremes and natural hazards. This requires a better understanding of tempo-spatial characteristics of natural hazards and also the interactions between different hazards in a changing climate. A combination of climate events (e.g., high temperatures and high humidity, or low precipitation and high temperatures) may cause a significant impact on the ecosystem and society, although individual events involved may not be severe extremes themselves – a notion known as compound event (e.g., extreme rain over burned areas, combined ocean and terrestrial flooding). This presentation focuses on three different types of compound events including drought-heatwaves, sea level rise-terrestrial flooding, and meteorological-anthropogenic drought. I present different methodological frameworks and perspectives for detecting, modeling, and risk assessment of compound and cascading events. I then discuss new frameworks for attribution of compound hazards.
References
AghaKouchak, A., Farahmand, A., Melton, F.S., Teixeira, J., Anderson, M.C., Wardlow, B.D., Hain, C.R., 2015a. Remote sensing of drought: Progress, challenges and opportunities. Rev. Geophys. 53, 452–480. https://doi.org/10.1002/2014RG000456
AghaKouchak, A., Feldman, D., Hoerling, M., Huxman, T., Lund, J., 2015b. Water and climate: Recognize anthropogenic drought. Nature 524, 409–411. https://doi.org/10.1038/524409a
AghaKouchak, A., Huning, L.S., Chiang, F., Sadegh, M., Vahedifard, F., Mazdiyasni, O., Moftakhari, H., Mallakpour, I., 2018. How do natural hazards cascade to cause disasters? Nature 561, 458–460. https://doi.org/10.1038/d41586-018-06783-6
Cheng, L., AghaKouchak, A., Gilleland, E., Katz, R.W., 2014. Non-stationary extreme value analysis in a changing climate. Clim. Change 127, 353–369.
Zscheischler, J., Westra, S., van den Hurk, B.J.J.M., Seneviratne, S.I., Ward, P.J., Pitman, A., AghaKouchak, A., Bresch, D.N., Leonard, M., Wahl, T., Zhang, X., 2018. Future climate risk from compound events. Nat. Clim. Change 8, 469–477. https://doi.org/10.1038/s41558-018-0156-3